Abstract: Limestone calcined clay cement (LC³), consisting of ordinary Portland cement (OPC) clinker, calcined clay, limestone powder, and gypsum, has been considered a promising solution to current challenges in the cement and concrete industry, such as high carbon emissions, high energy consumption, and resource shortages. This study carries out a series of experimental investigations of LC³-based paste, mortar, and concrete, including microstructural analyses (e.g. hydration product characterization and pore structure analysis) and macro-scale testing (e.g. workability and mechanical properties), using raw materials from south China. The results show that, in LC³ paste, the replacement of clinker by calcined clay and limestone leads to an increased volume of small pores but decreased total volume of pores. The workability of LC³ mortar and concrete can be readily tailored using conventional superplasticizers. When designed for comparable 28-d compressive strength, the LC³ mortar and concrete tend to have lower early-age compressive strength, but comparable compressive strength and higher flexural strength than those of the OPC counterparts at late ages. This study also examines the bond-slip behavior between LC³ concrete and steel bars and finds that the bond strength is comparable to that of OPC concrete with the same 28-d compressive strength, but that the LC³ concrete-rebar interface exhibits higher bond-slip stiffness. These findings on LC³ concrete provide fundamental information and guidance for furthering the application of LC³ binder in structural concrete in the near future.

Key words: Limestone calcined clay cement (LC³); Hydration; Bond-slip; Mercury intrusion porosimetry (MIP); Scanning electron microscope (SEM); Bond strength

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